In general, a heat engine generates a thermal energy by fuel combustion. The heat engine converts a portion of the thermal energy to a mechanical energy and emits the other portion of the thermal energy. For example, the heat engine includes an internal-combustion engine, an external-combustion engine and a boiler. The heat engine is used as an essential power source in an industrial plant and used as a power source in a vehicle such as an automobile, a ship and an airplane.
Since the heat engine gains the thermal energy by fuel combustion, the heat engine emits an exhaust gas resulting from fuel combustion. The exhaust gas includes various hazardous substances. For example, the exhaust gas emitted from the automobile includes the hazardous substances such as carbon dioxide (CO2), carbon monoxide (CO), nitrogen compound (NO, NO2) and hydrocarbon (HC). Accordingly, the exhaust gas is emitted through a purification equipment so that the hazardous substances can be converted to one of carbon dioxide (CO2), water (H2O) and nitrogen (N2) by reaction with a catalyst such as platinum (Pt), palladium (Pd) and rhodium (Rh) in the purification equipment.
However, although the hazardous substances that are noxious to a human body are removed from the exhaust gas through the purification equipment, a carbon compound such as carbon dioxide (CO2), which is one of major environmental contamination substances, is not removed from the exhaust gas.
Since carbon dioxide occupying about 60% of greenhouse gases causes a global warming, endeavor and regulation on reduction in emission of carbon dioxide have been done through a convention on climate change. Recently, as a carbon emission rights trading market has been introduced, enterprises have to buy the emission rights when they can not reduce emission of carbon dioxide to an assigned target amount. Accordingly, competitive power of the enterprises that buy the emission rights is reduced due to increase in cost. Further, since the enterprises that achieve the assigned target amount in emission of carbon dioxide sell the emission rights corresponding to the reduction amount, they make surplus profits and obtain an environment-friendly image.
As a result, although every enterprise has been made an effort on development of reduction technology in emission of carbon dioxide, a prominent reduction technology in emission of carbon dioxide that is satisfactory in view of efficiency, economy, industrial utilization and field application is not developed.
In addition, a heat engine generally reuses a portion of the thermal energy having a temperature of about 1000° C. and the other portion of the thermal energy is emitted. Accordingly, the emitted heat energy of a relatively high temperature causes the greenhouse effect and the global warming with waste of energy.